The invention relates to the use of substances which are specific to CEACAM8 for the manufacture of a medicament for the prophylactic or therapeutic treatment of human autoimmune diseases and/or gout. Another object of the invention concerns the use of CEACAM8-specific substances for apoptosis induction in-vitro. The invention also relates to a method for screening substances which induce apoptosis and a method for inducing apoptosis in human granulocytes.
Granulocytes form the first and fastest line of defense against pathogenic infections. Upon arrival at the site of infection, they participate in the inflammatory reaction by phagocytosis and intracellular killing of bacteria, the production of inflammatory mediators and the release of cytotoxic enzymes and proteins. An unfortunate consequence of granulocyte recruitment represents the ability to cause collateral tissue damage during acute inflammation, and thus their activity and their half-life must be tightly controlled. Their survival is limited by apoptosis, a process that is critical for the resolution of inflammation. Apoptosis refers to a programmed cell death, whereby the cell executes a cell's intrinsic suicide program. It is thought that the apoptosis program is evolutionarily conserved among virtually all multi-cellular organisms. In many cases apoptosis may be a default program that must be actively inhibited in healthy surviving cells. Cell death by apoptotic processes comes along with an early manifestation of membrane asymmetry which is detected as appearance of phosphatidylserine on the outer leaflet of the plasma membrane, preceding DNA fragmentation, plasma membrane blebbing and the loss of membrane integrity. Normally, granulocytes are short-lived cells with a half-life of only six to twenty hours in circulation undergoing apoptosis subsequently. The decision by a cell to submit to apoptosis is influenced by a variety of regulatory stimuli and environmental factors. Both pro-apoptotic and anti-apoptotic agents alter the lifespan of granulocytes. It is known that physiological activators of apoptosis include tumor necrosis factor (TNF), Fas ligand (FasL), transforming growth factor A, the neurotransmitters glutamate, dopamine, N-methyl-D-aspartate, withdrawal of growth factors, loss of matrix attachment, calcium and glycocorticoids. Damage-related inducers of apoptosis include heat shock, viral infection, bacterial toxins, the oncogenes myc, rel and E1A, tumor suppressor p53, cytolytic T-cells, oxidants, free radicals and nutrient deprivation. Furthermore, therapy-associated apoptosis inducers are known including gamma radiation, UV radiation and a variety of chemotherapeutic drugs, such as cisplatin, doxorubicin, bleomycin, methotrexate and vincristine. In particular, FasL and staurosporine are potent inducers of apoptosis in granulocytes. Contrary, pro-inflammatory cytokines, e.g. GM-CSF, G-CSF and IL-6, can increase the number of polymorphonuclear granulocytes (PMN) by prolonging their lifespan. Membrane-anchored proteins like PECAM-1 are also described to regulate apoptosis in granulocytes. It is a disadvantage of all mentioned inducers that they affect diverse cell types, thereby preventing the selective targeting of cells.
It was shown that molecules of the carcinoembryonic antigen (CEA) family regulate distinct cellular processes. WO 01/013937 A1 discloses peptides which are capable of modulating several cell functions by docking to CEACAM proteins, such as proliferation, differentiation, adhesion, cell activation and blocking. In detail, the peptides are directed to immune cells, e.g. leukocytes and their subtype of neutrophils. The peptides could be used as antibacterial, anti-inflammatory or anti-neoplastic agents for treating matching diseases. However, the agents are neither able to distinguish between single members of the CEA family nor to exert an influence on a specific cell activity, such as apoptosis. The treatment of mammals with these peptides is accompanied by severe adverse effects. Further specific peptides to the same CEA family target and for the same purpose are claimed in WO 2002/068601 A2. They can additionally alter an immune response which is to be specified yet.
WO 03/002764 A2 teaches a method which allows to identify therapeutically useful compounds by detecting the expression of glycoprotein antigens of the CEACAM family. The compounds can be applied in tumor prevention by increasing the sensitivity of cells to apoptosis which is controlled via gene expression. The loss of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) expression is associated with the loss of apoptosis and vice versa. Therefore, pharmaceutical agents mainly affect growing cells or other expressing cells whereas medical indications involving resting cells are excluded. Available CEACAM8 is not a target. Furthermore, the transmembrane bound glycoprotein CEACAM1 is abundantly expressed in epithelia, vessel endothelia and leukocytes, there mediating a variety of cell processes, such as proliferation, cell migration, tumor growth and angiogenesis. Pre-assigned adverse effects are of disadvantage and enhanced once more by the docking ability of the compounds to other members of the CEA family, particularly to CEACAM7.
It has been recently shown by Singer et al. (2005) Eur. J. Immunol. 35 (6), 1949-1959, that CEACAM1 triggers the delay of spontaneous and FasL-induced apoptosis in rat granulocytes. That means the ligand binding to CEACAM1 prolongs the lifespan and consequently the functional capacity of granulocytes during an inflammatory reaction. The publication does not provide a tool to prevent a persistent immune response which is especially undesired in autoimmune diseases.
Autoimmune diseases concern an exaggerated immune reaction directed against the body's tissue which is aberrantly assigned as deleterious target. Severe inflammations are caused by autoimmune diseases which finally result in the damage of the affected organs. Common autoimmune diseases include autoimmune hepatitis, chronic gastritis, diabetes mellitus type 1, Morbus Crohn, Multiple Sclerosis, arthritis, psoriasis or rheumatism. Several therapeutic treatments are applied which success has to be evaluated in each case. An abatement of symptoms and a reduction of acute attacks are achieved by cortisone. However, cortisone treatment is associated with a couple of adverse effects restricting its administration to a short period. Furthermore, the weakening of the immune system is known by immune suppressive agents. For instance, methotrexate is used to treat Multiple Sclerosis or rheumatism. Changes in hemogram, gastrointestinal dysfunction, nausea, diarrhea, tumor induction, alopecia and weight reduction arising from methotrexate administration are of disadvantage.
US 2004/0185053 A1 teaches an immunoconjugate for treating autoimmune diseases, for example, which conjugate comprises a targeting moiety, a chemotherapeutic moiety and a linker binding each other. Among others, the immunoconjugate exploits the occurrence of CD66b on the surface of abnormal cells for drug targeting by antibodies. The targeting moiety and therapeutic moiety are clearly distinguished and inevitably associated. The document only addresses the question of developing novel linkers, but utilizes drugs known in prior art and having such adverse effects as already discussed.
Therefore, the technical problem forming the basis of the present invention is to provide further substances for the treatment of human autoimmune diseases, especially such substances which improve the efficacy and minimize adverse effects.